Antao V P, Gray D M, Ratliff R L
Program in Molecular and Cell Biology, University of Texas, Dallas, Richardson 75083-0688.
Nucleic Acids Res. 1988 Jan 25;16(2):719-38. doi: 10.1093/nar/16.2.719.
On the basis of circular dichroism (CD) data, we have now identified six different conformational states (other than the duplex) of poly[d(A-G).d(C-T)] at pH values between 8 and 2.5 (at 0.01M Na+; 20 degrees C). Three of these structural rearrangements were observed as the pH was lowered from 8 to 2.5, and three additional rearrangements were observed as the pH was raised from 2.5 back to neutral pH. The major components of the six conformational states were defined using appropriate combinations of the CD spectra of the duplex, triplex, and denatured forms of this polymer, as well as the CD spectra of the individual single strands and their respective acid-induced self-complexes. Our results show that the acid-induced rearrangements of poly[d(A-G).d(C-T)] include not only the poly[d(C+-T).d(A-G).d(C-T)] triplex, but also include the poly[d(C-T)] loop-out structure and a self-complexed form of the poly[d(A-G)] strand that is pH-dependent.
基于圆二色性(CD)数据,我们现已确定了聚[d(A-G).d(C-T)]在pH值介于8至2.5之间(0.01M Na⁺;20℃)时的六种不同构象状态(双链体除外)。随着pH值从8降至2.5,观察到其中三种结构重排;随着pH值从2.5升至中性pH值,又观察到另外三种重排。使用该聚合物双链体、三链体和变性形式的CD光谱的适当组合,以及各个单链及其各自酸诱导的自复合物的CD光谱,定义了六种构象状态的主要成分。我们的结果表明,聚[d(A-G).d(C-T)]的酸诱导重排不仅包括聚[d(C⁺-T).d(A-G).d(C-T)]三链体,还包括聚[d(C-T)]环出结构以及pH依赖性的聚[d(A-G)]链的自复合形式。